Imaging moving structures such as cardiac tissue walls and nearby medical instrumentation presents a unique set of problems not ideally addressed in three dimensions by conventional devices employing imaging modalities such as magnetic resonance imaging (“MRI”), computed tomography (“CT”), and ultrasound. One the challenges with MRI and CT imaging modalities is related to the requisite sampling rate useful for monitoring three dimensional motion of tissues moving with relatively high frequency and high amplitude motion, such as cardiac tissues. Sophisticated arrays of ultrasound transducers, available in products from suppliers such as Koninklijke Philips Electronics N.V., may be utilized to produce real-time three-dimensional visualization of relatively high-frequency, high-amplitude moving tissues such as cardiac tissues, but such devices are generally large in size and configured for transthoracic access to such tissues.
Maintaining transthoracic or similar contact and access during a procedure involving the heart below or other similarly situated tissue of the body is difficult if not impossible, depending upon the particular procedure. Smaller ultrasound systems have been designed and utilized for catheter-based deployment to provide more direct access for imaging tissues and providing instrument guidance feedback. Products such as the side-firing ultrasound catheter sold by Siemens Corporation under the tradename “AcuNav™”, the diagnostic ultrasound catheters sold by EP-Technologies-Boston-Scientific Corporation under the tradename “Ultra ICE™”, or the intravascular ultrasound imaging catheters sold by Jomed Corporation under the tradename “Avanar™”, for example, may be combined with software and automated position advancement technology from suppliers such as TomTec Imaging Systems GmbH of Munich, Germany, to produce three-dimensional renderings of various tissue structures of the body, such as vascular and cardiac tissue structures from endovascular and endocardial perspectives. The ultrasound transducer hardware comprising such systems generally is fairly simple due to size constraints, and this simplicity is advantageous for device complexity, cost, and disposability reasons. Use of these conventional systems to produce three-dimensional renderings, however, generally requires hybridizing or “gluing together” datasets captured over relatively long periods of time employing assumptions of tissue motion cycle homogeneity to produce three-dimensional renderings.
In medical fields such as remotely actuated or minimally invasive surgery, it is desirable to have accurate, timely information regarding the relative positioning of remotely deployed medical devices and nearby tissue structures such as tissue walls. For example, one may want to biopsy a portion of a tissue wall with a mechanical end effector, inject something into and not beyond a tissue wall, or touch a tissue wall with an electrode, and have some confirmation, preferably in three-dimensions, of the relative positioning between pertinent objects during such procedures. There remains a need for a means to produce timely three-dimensional relative positioning data utilizing a noninvasive modality such as ultrasound via relatively simple structures and techniques.